cassan



Jan. 31, 1956 J. H. F. cAssAN FURNACES, AND MORE PARTICULARLY COKE OVENS4 Sheets-Sheet 1 Filed April 25, 1951 Inventor: Jean Horn-1 Francoiscaum Jan. 31, 1956 J c ss 2,733,197

FURNACES. AND MORE PARTICULARLY COKE OVENS Filed April 23, 1951 4Sheets-Sheet 2 Fig. 3

Inventor: Jean. Henri Francois Cassan.

Jan. 31, 1956 J. H. F. cAssAN FURNACES, AND MORE PARTICULARLY com: OVENSFiled April 23. 1951 4 Sheets-Sheet 3 Inventor: J'aan Henri FrancoisCanaan Jan. 31, 1956 J. H. F. CASSAN FURNACES, AND MORE PARTICULARLYCOKE OVENS Filed April 23, 1951 4 Sheets-Sheet 4 Inventcr Joan Henri FrvStts FURNACES, AND MURE PARTICULARLY CGKE OVENS This invention relatesto the recovery of the heat content of the flue gases in furnaces andthe like, and to the utilisation of such heat content for heating thecombustion gases.

Coke ovens and similar furnaces generally are provided with horizontalchambers separated by internallyheated recessed dividing walls,hereinafter termed partitions. The partitions are divided into usuallyvertical flues in which the combustion of the fuel gas takes place.

Gaseous fuels of widely varying types may be used, such as lean gas, e.g. producer gas and blast-furnace gas. In the case of blast-furnace gasfor instance, it is known that the complete combustion of such fuelrequires a volume of air approximately equal to the volume of gas.

Throughout the ensuing description and claims, the followingconventional terms will be used for the sake of atent O clarity andconvenience: viz., the word gas will be used to designate any type ofcombustible gas or mixture of gases; air will be used for designatingthe oxygenproviding medium; and waste or flue gases will signify theresult of the combustion of the gas and air mixture.

The invention employs the general method of recovering the heat contentof the waste gases issuing from the heated partitions of the furnace bythe conventional process involving periodic reversal of the flow ofgases, in which each burner is connected with two heat-recovering cells,one cell serving to heat the gas and the other heating the air fordefinite periods of time, while each cell of the pair alternately is fedwith hot Waste gases during a derinite period after it has yielded upits heat content to the gas and air.

As a general rule, the heat-recovery or regenerating cells are locatedbelow the furnace structure which includes the carbonizing chambers andthe heated partitions. That part of the furnace structure which comprisethe waste heat recovery cells is diflicult to design and constructbecause the cells are comparatively many and must communicate with theheated partitions which separate the adjacent carbonizing chambers.

A section of the furnace, which may be termed the intermediate section,is located between the bottom of the carbonizing chambers and the heatedpartitions, and the top of the waste-heat recovery cells. Thisintermediate furnace section, in present furnace construction, isusually traversed by ducts conveying the gas, air and/or waste gas, andthe designs of such ducts is always more or less intricate. Thisarrangement results in a whole set of drawbacks especially owing to thefact that this intermediate section, which is relatively fragile, issubjected to high internal stresses due to the temperature gradientsprevailing between its top and the base of said intermediate section.Moreover, the temperature at the base of the intermediate section issubjected to rapid variations because the direction of gas flow isperiodically reversed so that it is alternately traversed by the gas andby fresh air, and then by the hot flue gases.

Within a comparatively short period of time, accordingly, the structureof the intermediate becomes damaged and cracks appear in the brickworkor other masonry. These cracks are rather large despite the use ofexpansion joints and sliding joints. As a result of these cracks, airand/or gas leak back into the flue gases, and pre-combustion may occur,which in all cases will reduce the efliciency ratio of the combustion,and will in many instances impair the strength of the furnace structureowing to excessive local temperature elevations;

It is a general object of this invention to overcome these drawbacks andto provide a waste heat recovery or regenerating furnace of the typedescribed in which the service life is increased, especially in thoseportions thereof which were most liable to rapid damage heretofore.

Further objects of the invention, as well as the characteristic featuresthereof will appear as the description proceeds.

In the accompanying drawings, one exemplary embodiment of the furnaceaccording to the invention is illustrated for purposes of indication andnot of limitation.

Fig. 1 is a diagrammatic sectional view of a coke oven, in accordancewith the invention, on a vertical plane normal to the centre plane ofthe combustion chambers and in which cross over flues are provided.

Fig. 2 is an isometric view, with parts broken away, of a waste-heatrecovery unit or cell.

Fig. 3 is a section on line III-III of Fig. 1.

Fig. 4 is a section on line IVIV of Fig. 3, and modified to illustratethe application of the invention to coke ovens having hairpin flues.

Fig. 5 is a section on line VV of Fig. 3 or 4.

Fig. 6 is a section on an enlarged scale showing structural details ofthe gasand air-delivery ducts and the waste gas-discharge ducts or fluesat the base of the Wasteheat recovery units.

Fig. 7 illustrates the arrangement of four waste heat recovery orrecuperating units; and

Fig. 8 is an enlarged view of part of the sectional view of'Fig. 3.

As shown in the drawings, Fig. 1 diagrammatically illustrates in crosssection a coke oven having the carbonizing chambers i in which verticalrecessed heated partitions 2 are provided; The upper furnace structureincluding the carbonizing chambers 1 and partitions 2 is supported onwalls 3 which subdivide the lower furnace structure in which the wasteheat recovery cells are arranged. These recovery cells or units 4 mayfor example consist, as shown, of shells of refractory or firebrickmaterial similar to smoke flues commonly used in building construction.

According to the invention, the waste heat recovery or regeneratingunits rest upon a base or hearth 5 provided at the bottom of the furnaceand do not contact the walls 3 at any point of their height. Thus thewaste heat recovery units will not be subjected to any strains shoulddistortion appear in the walls 3. However, the gaps 6 between therecovery brickworks 4 and the walls 3 may be filled with a suitablecompressible filling material such as refractory mineral wool or thelike. Pulverulent filler material such as crushed clay may also be usedfor this purpose.

Extending below the recovery cells 4 are ducts 7 and 8 through which thevarious gaseous media flow in the operation of the furnace. Thus, for agiven period of operation, gas may flow through the duct 7 on the leftof Fig. 1 and air through the duct 8 on the left of Fig. 1, while duringthe same period waste gas will be flowing through both the ducts 7 and 8on the right of the figure. During the next stage of operation, the flowis reversed so that gas and air will be flowing through the ducts underthe right-hand recovery cell, whereas waste gas will be found under theleffihand recovery cell.

Each recovery cell is filled with suitable filling elements such assmall plates 9 of refractory material stacked in crisscross relation andserving to store heat. These heat-absorbing plates or similar fillingelements may be obtained in any of the various conventional forms.

Asshown in Fig.2, each cell is formed or provided with an'upwardlytapering top section 10, and each pair of adjacent tapering tops 10constitutes a burner which fits into a recess of corresponding form 11formed in the furance structure. It can be seen that, during thoseperiods when any individual recovery cell has an upward flow of gas andair therethrough, the gas and the air flowing upwards towards the burnerportions 10 to heat the corresponding partition 2, a suctionis createdin the recesses it due to the gas flowing from the recovery cell. On theother hand, during those stages where the cell has a downward flow 'ofwaste gases therethrough, that is while the'heated waste gases areflowing down into the recovery cell, superatmospheric pressure prevailsin the cavities' 11. It follows that, if the walls of the recovery cells4 are not totally airtight, the air and gas leaking through the wallsare drawn upwards and will be burned up in the spaces between therecovery cells and the walls 3, and the resulting waste gases are alsodrawn up with the general flow of waste gases and will contribute toheating the partition 2. In the same way, during periods in which thecells are being traversed by waste gases, any waste gases that may leakinto the spaces 6 are simply recycled without any deterimental effect onthe heating.

If desired however, each waste-heat recovery cell may be individuallyencased in a thin casing of high temperature resistant plating 13 asshown in Fig; 2.

The individual heat-recovery units, it may be seen, have each acomparatively small cross-section, their heat-storage capacity beingnevertheless sufficiently large owing to the provision of the fillingplates or elements 9.

As already stated, the heat-recovery units are all placed upon thehearth 5 under which all of the flues and ducts are provided throughwhich the gas, air and waste gases flow.

Fig. 3 illustrates in horizontal cross section part of the structure ofthe furnace. To facilitate the ensuing description, it will beconvenient to define each individual heat-recovery unit with referenceto a pair of coordinates axes Ox-Oy. face of the furnace battery, whileOy is parallel to the central plane of the carbonizing chambers 1. Asshown, the recovery or regenerator units are grouped in fours, and eachgroup of four is divided from the adjacent groups, on two sides by thefurnace walls 3 parallel to y and on the other two sides by thepartitions 13 parallel to 0y, which latter partitions may either beintegral with the walls 3 or assembled thereto as by grooved joints. Inthe ensuring disclosure, the ranks of aligned groups of recovery unitsextending parallel to the axis Oy are designated as files, whereas theranks of aligned groups parallel to axis Ox are described as ranks. Anindividual recovery unit will be designated by the letter R followed bya sufiix consisting of its file number followed by its rank number. Thusthe unit designated X is called the unit R(3-3). The unit shown at Y isunit R(46); and the unit Z is unit R(4).

The furnace can be so constructed that beneath each file of recoveryunits there extends a duct which hereinafter will be represented by theletter K followed by a suffix numeral designating the particular fileunder which it extends (Fig. 3).

A further conventional code used in Fig. 3 is that referring to therepresentation of the various media flow- Axis Ox is parallel to thefront 4 t ing through the ducts of the recovery units. As shown in thefigure, vertical hatch-line represent gas flow, horizontal linesrepresent air flow, while the crosshatches represent the waste gases.Thus, Fig. 3 illustrates the condition as to the media flowing throughthe recovery units during one particular stage of operation of thefurnace. After reversal of flow, those units through which air or gaswas flowing in the preceding period will now be having waste gasesflowing therebetween, while those units in which waste gases wereflowing in the previous stage will now have either air or gas flowingtherethrough depending on the file to which they belong.

It can be seen that the communicating duets can be so established that,at any instant taken as a time reference, the ducts K(11z4+1) will beconveying air, the air, the ducts 1((1114-1-2) will be conveying gas,and the ducts K(m4+3) and K(m4) will be conveying waste gases, in beinga parameter which can assume any integral value or may be zero.

After flow-reversal, the ducts K0224) will be conveying air, ductsK(m4+3) gas, and ducts K(m4+l) and K(m4+2) will be delivering wastegases.

It will be noted that at each end of the furnace assembly an additionalduct must be provided, in which the condition at each stage will bedetermined by its file number; thus the duct KO will correspond infunction to a duct K0114) in which 122:0.

The connections are provided as follows:

The ducts of the files (1214) only communicate with the recovery unitshaving the ranks (I14) and (124+l) in the same file and in the nextfollowing file.

The ducts of file (m4+1) only communicate with the recovery units ofranks (124+2) and (n4-l-3) in the same file and in the next precedingfile.

The ducts of file (m4]2) only communicate with the units of ranks(1144-2) and (114+3) in the same file and in the next units followingfile.

And the ducts of file (m4+3) only communicate With the units of ranks(124) and (n4+l) in the same file and in the next preceding file.

As a result of the flow connections just described, it will be seen thatthe regenerator units are cfiectively supplied in thepreviously-described manner at any stage of operation of the furnace.

It should be understood that the system of connections just describedprovides only one example out of many, and that other suitable networksor flowsheets may be devised in connection with a furnace arrangementaccording to the invention, the basic idea of which is the provision ofa furnace in which the recovery units are spaced from the interveningwalls, and are supplied with gas and air and/or waste gases exclusivelyfrom their bottom ends.

Figs. 4 and 5 are diagrammatical vertical sections of a coke ovencomprising suitable connecting meansfor realizing the flow networks ofthe type specified above. In order to save space in the drawings andsimplify the illustration, one vertical tier of the superstructure hasbeen omitted in Figs. 4 and 5. Furthermore, in these two figures,hairpin flues are shown in place of the crossover fines of Fig. l, toillustrate the application of the invention to both types of coke ovens.The arrows shown in the heated recessed partitions indicate thedirection of flow of the media at a particular instant taken as a timereference. The arrows in broken lines indicate the direction of flow ofthe media after reversal. It will be observed in Fig. 4 that only therecovery units of the ranks (n4+2) and (114+3), that is e. g. the unitsR(6-2), R(6-3) communicate direct with the duct K6 which, at the timetaken as a reference, is conveying gas. The apertures 14 which areadjacent the openings of the units of ranks (n4+2) and (n4+3.) providecommunication with the units of similar ranks in the file numbered 7and, generally speaking, in any file in which the reference number is InFig. ducts are shown which fulfill similar functions with respect to thefiles 5 and 4. It is further seen in this figure that the heat-recoveryunit R(42) is supplied with air from the duck K5 through the channel 15,and unit R(32) is supplied with gas through channel 14.

In Fig. 4, it is seen that the units R(61) R(64) and R(65), that is theunits of ranks (n4+1) and (n4) which are not in communication with theduct K5, are nevertheless provided at their base with an aperture 16which connects them with the duct K7, which at the reference instantunder consideration is conveying waste gases.

As a final result of the arrangement described, it will be seen that thecrossings between the ducts and fines, regardless of the particularnetworks under consideration, are always located in the lower section ofthe'brickwork structure, which is thus kept at a low temperature andconsequently protected against dislocation due to thermal expansion andcontraction. In conventional furnaces of comparable type, theintermediate furnace section that is the section situated between thecarbonizing chambers and the top of the heat-recovery units, has atleast part of the ducts and fines incorporated in it.

Fig. 6 illustrates in detail the bottom section of a heatrecovery orregeneration unit, and this figure forms a fragment of the sectionalview shown in Fig. 5. More specifically, Fig. 6 shows the bottom part ofunits R(62) and R(72) at the reference instant. Unit R(62) communicateswith the duct K6 through a venturi 17, and unit R(7-2) communicates withthe same duct K6 through a conduit 14 which terminates in a venturi l8.Delivering into the venturi 17 and into the conduit 14 are gas supplylines 19 and 20 respectively. Each gas supply line is provided with acontrol valve 21, 22. The lines 19 and 20 are connected to a main supplyline 23.

The duct K7 does not communicate with either unit R(62) and R(72) butdoes communicate with, e. g., the units R(6-t) and R(7-4) throughventuris similar to the venturis i7 and 18. At the reference time theduct K7 is conveying waste gases while the line 24 is not supplied withgas.

As stated previously, the invention is herein described moreparticularly as applied to a furnace fired with lean gas, for exampleproducer gas. It is to be understood however, that the invention is alsoapplicable to furnaces fired with richer gas fuel, for examplecarbonization gas or coal gas, natural gas, etc. Moreover, the inventioncan be embodied in a furnace designed for firing with rich gas alone orin a furnace capable of being fired either with rich or lean gas. ifrich gas is exclusively used for firing, the adjacent two heat recoveryunits in a common rank which otherwise would have been used forreheating gas and air, may be combined into a single unit.

If on the other hand the furnace is to be heated selectively with richor lean gas, the procedure would be to construct a furnace of the typefired with lean gas, and means for supplying the burners with rich gaswould simply be added thereto.

A method will now be described for constructing a furnace according tothe invention. The hearth 5 is first constructed which is to support theheat-recovery units. In this hearth the ducts K are formed, as well asthe conduits 14 and 15 and venturis 17 and 18. The hearth is built up tothe level of the lower surface of the recovery units. Advantageously thehearth is made of slightly refractory concrete. The ducts K are providedby incorporating e. g. wooden cores about which the concrete is cast,while the conduits i4, 15 and the venturis 17 and 18 of more intricateconfiguration can be provided for by including forms made of thinpress-formed metal sheets. Of course, the ducts K may also if desired beobtained by the use of press-formed metal forms rather than woodencores. After the concrete has set the metal forms are left in placewhile the wooden cores, if any, are

-;withdrawn. Such procedure is very simple since it only units 4 areeasily positioned upon the base plate 25.

requires the positioning of the metal forms which-do not in any wayimpede the operation of the furnace.

Next, the heat-recovery or regenerator units 4 are placed in groups offour upon the hearth 5. Preferably, the groups of recovery units may beprefabricated in the following manner. Upon a metal, e. g. cast ironbase plate 25 (Fig. 7), the casing sections are stacked above apertures26 formed in the base plate 25. The apertures 26 are to correspond withthe various venturis of the hearth 5.

On each side of the hearth bosses 27 are provided, formed withscrew-threaded openings which are each to receive one end of a screw rod28. The two rods 28 are interconnected at their tops by a cross member29 provided at its midpoint with a hoisting ring 30. Four such rods maybe provided if desired instead of two. The rods 28 may further be madeto support a thin metal plate 31 of refractory alloy extending from theplate 25 to the base of the taper top burner sections 10. The verticalmargins of the metal plate 31 are curved as at 33 to pass around therods 28 (Fig. 8) and are brought into overlapping relation with thecorresponding vertical margins of the similar plates 31 provided in theadjacent group of re covery units. Before positioning the groups of heatrecovery units spacer boards 34 of compressible material are appliedagainst both sides of the plate 31 and further boards are placedextending perpendicularly therefrom, as shown. This material may be anagglomerated combustible material such as cork, wood fibre or felt,adapted to burn up at the first operation of the furnace. Thus theboards 34 serve to position the groups of heat recovery units and willdisappear in due course, without leaving any objectional residue, thusproviding the desired spacing between the outer surfaces of the heatrecovery units and the surrounding furnace structure. However, asalready stated, in some cases a non-combustible, re-

fractory compressible filling material may be provided instead of or inaddition to the said combustible boards 34. Suitable refractory fillingmaterials may include cellular concrete, porous brick, asbestos fibreand the like.

Once the boards 34 have been positioned, the recovery As shown, theunits consist of stacked hollow members in which suitable heat-storagefilling elements are arranged. After the four recovery units have beenmounted, they are surrounded with spacer boards 35 of compressiblematerial similar to the previously described spacer boards 34, and whichalso may or may not be combustible as desired, so that a solid compactstructure is obtained, only having the margins 33 of the sheet 31projecting from the opposite sides thereof as previously described. Forgreater strength, this block is then preferably reinforced by metalstrips or wires hooped or looped around it. For this purpose a metal maybe used which has a melting point lower than the furnace operatingtemperature, e. g. aluminum, so that it will melt or burn without givingout any substances liable to impair the proper performance of therefractory concrete.

To prevent dislocation of the prefabricated block including the fourheat-recovery units during transporta-- tion, a rigid plate may beprovided spaced above the burner apertures 10, said plate being providedwith a yielding lining such as felt, and being held in place by means ofthe cross-member 29 and rods 28. The block can then easily be engaged bymeans of the lifting ring 30 with suitable hoisting apparatus. Beforethe block is set into place upon the hearth 5, the hearth surface shouldbe perfectly leveled and have a coating of a suitable grout spread overit in order to seal the joints. The rods 28 are then unscrewed andwithdrawn.

A similar procedure is followed with each of the other regeneratorassemblies 4. The projecting margins 33 of the plates 31 are made tooverlap each other partially while yet allowing a small spacing betweenthem to allow for concrete expansion. This space 36 may be filled inwith a compressible combustible material, such as corrugated cardboardor the" like;

After all of the recovery blockshave thus been positioned, suitableforms are placed on the front surface and sides of the furnace structureand refractory concrete is poured into the spaces between the adjacentblocks. This provides concrete walls which form the under-structure ofthe furnace battery. The concrete is poured substantially to a levelflush with the base surface of the tapering burner sections 10. Thebuilding of the furnace is then proceeded with in the usual way in orderto provide the carbonizing chambers and the heated hollow partitionwalls.

It is to be understood that the invention is not restricted to thespecific details illustrated and described herein. Thus for example,instead of the compressible material from which the boards 34 are made,a compressible coating material may be used under coating the outersurfaces of the regenerator block 4. Moreover the compressible andcombustible material forming the spacer boards between the adjacentregenerator blocks 4 during the construction of the furnace may beprovided in the form of a composition containing an easily fusiblematerial such as an enamel which after combustion of the boards will bedeposited in the form of a gas-tight coating over the recuperatorsurfaces.

While the invention has been described with specific reference to acoking oven, it is to be expressly understood as being applicable to anyindustrial furnace incorporating waste-heat recuperating means therein.

What I claim is:

1. A coke oven type furnace comprising a tier of combustion chambers andheating fiues about said chambers, a lower tier of heat regenerators,each of said regenerators being associated with a corresponding one ofsaid heating flues and including at least two vertical casingscontaining gas-pewious stacked, heat-accumulating material, each of saidcasings terminating, at its upper end, in a tapered portion forming arelatively narrow opening communicating with said corresponding heatingflue, a base structure defining a seating for each casing at the bottomof said regenerators, a conduit in said base structure for selectivelyand alternatively receiving reversed flows of air and fuel and of wastegas, respectively, and a wall structure in said lower tier about thecasings of each regenerator conforming with the external configurationof said casings and being spaced from the latter to define spaces aroundthe casings of each regenerator acting as injectors to draw any gasesleaking into said spaces from adjacent regenerators into the relatedflue when air and fuel pass upwardly through said casings from therelated conduits and out through said tapered portions of the casings.

2. A coke oven type furnace comprising a tier of combustion chambers andheating fluesabout said chambers a lower tier of heat regenerators, eachof said re generators being associated with a corresponding one of saidheating flues and the heating flues of adjacent regeneratorscommunicating with each other at least at the upper ends of the flues,each of said regenerators including at least two vertical casingscontaining gas-pervious stacked, heat-accumulating material, each ofsaid casings terminating, at its upper end, in a tapered portion forminga relatively narrow opening communicating with the corresponding heatingflue, a base structure defining seatings for said casings at the bottomof said regenerators, said base structure having conduits extendingtherethrough from the exterior and opening through said seatings intoeach of said casings, said conduits being arranged to alternatively feedair and fuel and to receive waste gas from the related casings and sothat the conduits associated with the casings of one regenerator willfeed air and fuel thereto while the conduits associated with the casingsof the regenerator having its flue in communication with the flue ofsaid one regenerator will receive waste gas from the related casings,and a wall structure in said lower tier about the casings of each regenerator and segregating said casings from the casings of the adjacentregenerators, said wall structure conforming with the externalconfiguration of said casings and being spaced from the latter to definespaces around the casings of each regenerator acting as injectors whenair and fuel is fed to the casings so that any waste gas then leakinginto said spaces from adjacent regenerators is drawn from said spacespast the tapered portions of the casings and out through thecorresponding flue, while air and fuel leaking into said spaces fromadjacent regenerators when waste gas is being withdrawn through saidconduits passes along with the waste gas through said conduits.

References Citedin the file of this patent UNITED STATES PATENTS 734,457Engels July 21, 1903 1,099,932 Peiter June 16, 1914 1,510,857 MunsterOct. 7, 1924 1,720,958 Jacobus July 16, 1929 1,994,637 Doyle Mar. 19,1935 2,008,658 Otto July 16, 1935 2,098,013 Pavitt Nov. 2, 19372,132,641 Otto Oct. 11, 1938 2,216,983 Otto Oct. 8, 1940 2,350,813Philipsen June 6, 1944 2,458,480 Pinckard Jan. 4, 1949 2,623,846 RobertDec. 30, 1952 FOREIGN PATENTS 650,348 Great Britain Feb. 21, 1951

1. A COKE OVEN TYPE FURNACE COMPRISING A TIER OF COMBUSTION CHAMBERS ANDHEATING FLUES ABOUT SAID CHAMBERS, A LOWER TIER OF HEAT REGENERATORS,EACH OF SAID REGENERATORS BEING ASSOCIATED WITH A CORRESPONDING ONE OFSAID HEATING FLUES AND INCLUDING AT LEAST TWO VERTICAL CASINGSCONTAINING GAS-PERVIOUS STACKED, HEAT-ACCUMULATING MATERIAL, EACH OFSAID CASINGS TERMINATING, AT ITS UPPER END, IN A TAPERED PORTION FORMINGA RELATIVELY NARROW OPENING COMMUNICATING WITH SAID CORRESPONDINGHEATING FLUE, A BASE STRUCTURE DEFINING A SEATING FOR EACH CASING AT THEBOTTOM OF SAID REGENERATORS, A CONDUIT IN SAID BASE STRUCTURE FORSELECTIVELY AND ALTERNATIVELY RECEIVING REVERSED FLOWS OF AIR AND FUELAND OF WASTE GAS, RESPECTIVELY, AND A WALL STRUCTURE IN SAID LOWER TIERABOUT THE CASINGS OF EACH REGENERATOR CONFORMING WITH THE EXTERNALCONFIGURATION OF SAID CASINGS AND BEING SPACED FROM THE LATTER TO DEFINESPACES AROUND THE CASINGS OF EACH REGENERATOR ACTING AS INJECTORS TODRAW ANY GASES LEAKING INTO SAID SPACES FROM ADJACENT REGENERATORS INTOTHE RELATED FLUE WHEN AIR AND FUEL PASS UPWARDLY THROUGH SAID CASINGSFROM THE RELATED CONDUITS AND OUT THROUGH SAID TAPERED PORTIONS OF THECASINGS.